U.S. patent application number 12/146072 was filed with the patent office on 2009-01-01 for measurement methods and measuring equipment for flow of exhaust gas re-circulation.
Invention is credited to Eiichiro OHATA.
Application Number | 20090000367 12/146072 |
Document ID | / |
Family ID | 39809051 |
Filed Date | 2009-01-01 |
United States Patent
Application |
20090000367 |
Kind Code |
A1 |
OHATA; Eiichiro |
January 1, 2009 |
MEASUREMENT METHODS AND MEASURING EQUIPMENT FOR FLOW OF EXHAUST GAS
RE-CIRCULATION
Abstract
In measurement methods and a measuring equipment for flow of
exhaust gas re-circulation, in order to prevent performances of
exhaust, fuel efficiency, and power output from deteriorating due
to reasons such as large loss in pressure and time, a control delay
during an excessive operation, and reduction in an exhaust gas
re-circulation gas flow rate upon measuring an exhaust gas
re-circulation gas flow rate, an exhaust gas re-circulation gas
flow rate is measured by a plurality of measurement methods on the
basis of an intake air flow rate and pressure before and after a
heat exchanger installed at an exhaust gas re-circulation passage
and the measurement methods are carried out by performing a mutual
comparison of the measurement flow rates. Accordingly, it is
possible to measure the exhaust gas re-circulation gas flow rate
with high precise in a short response time without increasing loss
in pressure, and thus to improve performances of exhaust, fuel
efficiency, and power output.
Inventors: |
OHATA; Eiichiro; (Kasama,
JP) |
Correspondence
Address: |
MATTINGLY, STANGER, MALUR & BRUNDIDGE, P.C.
1800 DIAGONAL ROAD, SUITE 370
ALEXANDRIA
VA
22314
US
|
Family ID: |
39809051 |
Appl. No.: |
12/146072 |
Filed: |
June 25, 2008 |
Current U.S.
Class: |
73/114.74 ;
60/605.2 |
Current CPC
Class: |
Y02T 10/40 20130101;
F02B 29/04 20130101; F02D 41/0072 20130101; F02M 26/05 20160201;
F02D 41/1448 20130101; Y02T 10/47 20130101; F02D 41/1454 20130101;
F02M 26/47 20160201; F02M 26/22 20160201 |
Class at
Publication: |
73/114.74 ;
60/605.2 |
International
Class: |
G01M 15/10 20060101
G01M015/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 27, 2007 |
JP |
2007-168363 |
Claims
1. A measuring equipment for flow of exhaust gas re-circulation
comprising: a control valve which is provided in an exhaust gas
re-circulation passage of an internal combustion engine so as to
control a flow rate in the exhaust gas re-circulation passage; a
heat exchanger which cools exhaust gas re-circulation gas; pressure
sensors which measure pressure of the exhaust gas re-circulation
gas at two or more positions of the exhaust gas re-circulation
passage before and after the heat exchanger; a temperature sensor
which measures temperature of the exhaust gas re-circulation gas;
and an intake air flow sensor which is provided in an intake air
passage so as to measure a flow rate of intake air.
2. The measuring equipment according to claim 1, further
comprising: a first exhaust gas re-circulation gas flow measuring
unit which calculates a first exhaust gas re-circulation gas flow
rate on the basis of a sectional area of the exhaust gas
re-circulation passage of the heat exchanger, a phase-difference
time of a pressure waveform, and a distance of the exhaust gas
re-circulation passage between two or more different pressure
measurement positions measured by the pressure sensors; a second
exhaust gas re-circulation gas flow measuring unit which calculates
a second exhaust gas re-circulation gas flow rate on the basis of a
difference between pressure values measured at two or more
different measurement positions by the pressure sensors and the
sectional area of the exhaust gas re-circulation passage of the
heat exchanger; and a third exhaust gas re-circulation gas flow
measuring unit which calculates a third exhaust gas re-circulation
gas flow rate on the basis of a difference between the intake air
flow rate measured by the intake air flow sensor and a
predetermined value.
3. The measuring equipment according to claim 2, wherein when the
second exhaust gas re-circulation gas flow rate measured by the
second exhaust gas re-circulation gas flow measuring unit while
closing the control valve is a predetermined value or less, a
distance value of the exhaust gas re-circulation passage between
two or more different pressure measurement positions used for a
calculation of the first exhaust gas re-circulation gas flow
measuring unit is corrected so that the first exhaust gas
re-circulation gas flow rate measured by the first exhaust gas
re-circulation gas flow measuring unit becomes zero.
4. The measuring equipment according to claim 2, wherein when a
measurement flow rate difference between the third exhaust gas
re-circulation gas flow rate measured by the third exhaust gas
re-circulation gas flow measuring unit and the first exhaust gas
re-circulation gas flow rate measured by the first exhaust gas
re-circulation gas flow measuring unit is larger than a
predetermined value, a sectional area value of the exhaust gas
re-circulation passage of the heat exchanger used for a calculation
of the first exhaust gas re-circulation gas flow measuring unit is
corrected so that the measurement flow rate difference becomes
zero.
5. The measuring equipment according to claim 2, wherein when a
measurement flow rate difference between the third exhaust gas
re-circulation gas flow rate measured by the third exhaust gas
re-circulation gas flow measuring unit and the second exhaust gas
re-circulation gas flow rate measured by the second exhaust gas
re-circulation gas flow measuring unit is larger than a
predetermined value, a sectional area value of the exhaust gas
re-circulation passage of the heat exchanger used for a calculation
of the second exhaust gas re-circulation gas flow measuring unit is
corrected so that the measurement flow rate difference becomes
zero.
6. The measuring equipment according to claim 2, wherein one of the
first exhaust gas re-circulation gas flow measuring unit and the
second exhaust gas re-circulation gas flow measuring unit used to
measure the exhaust gas re-circulation gas flow rate is selected on
the basis of a difference between a predetermined value and a
quotient of a pressure difference between pressure values measured
at two or more measurement positions by the pressure sensors and an
amplitude of the pressure difference.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an exhaust gas
re-circulator for a diesel engine, and more particularly, to a
technique for appropriately measuring an exhaust gas re-circulation
gas flow rate.
DESCRIPTION OF RELATED ART
[0002] In order to reduce a discharge amount of nitrogen oxides of
exhaust gas generated from an internal combustion engine, it is
effective to restrict a combustion temperature by means of the
exhaust gas re-circulation. Particularly, in a diesel engine, an
exhaust gas re-circulation gas flow rate can be increased more than
that of a gasoline engine. However, when the exhaust gas
re-circulation gas flow rate is increased too much, a problem
arises in that fuel efficiency deteriorates and soot increases. For
this reason, it is necessary to appropriately maintain the exhaust
gas re-circulation gas flow rate in accordance with a driving
state. In addition, it is necessary to provide a measurement method
for measuring the exhaust gas re-circulation gas flow rate with
high precision in a short response time in order to cope with a
variation in driving state. For this reason, for instance,
JP-A-1-178760 discloses a technique for calculating the exhaust gas
re-circulation gas flow rate on the basis of the measurement value
of a gas density detector. Additionally, JP-A-2007-101426 discloses
a technique for calculating the exhaust gas re-circulation gas flow
rate by use of a hot wire type air flow sensor.
[0003] In the technique disclosed in JP-A-1-178760, it is not
appropriate to solve the above-described problems in that it takes
time to measure gas density. Meanwhile, in the technique disclosed
in JP-A-2007-101426, the thermal flow meter has a short response
time, but it is difficult to measure a counter flow, and
additionally, a heating resistor needs to be installed in a
passage, which causes pressure loss. As a result, a problem arises
in that the exhaust gas re-circulation gas flow rate decreases upon
installing sensors for measuring the exhaust gas re-circulation gas
flow rate.
BRIEF SUMMARY OF THE INVENTION
[0004] In order to attain the above-described object, according to
an aspect of the invention, there is provided a measuring equipment
for flow of exhaust gas re-circulation including: a control valve
which is provided in an exhaust gas re-circulation passage of an
internal combustion engine so as to control a flow rate in the
exhaust gas re-circulation passage; a heat exchanger which cools
exhaust gas re-circulation gas; pressure sensors which measure
pressures of the exhaust gas re-circulation gas at two or more
positions of the exhaust gas re-circulation passage before and
after the heat exchanger; a temperature sensor which measures
temperature of the exhaust gas re-circulation gas; and an intake
air flow sensor which is provided in an intake air passage so as to
measure a flow rate of intake air. The measuring equipment further
includes: a first exhaust gas re-circulation gas flow measuring
unit which calculates a first exhaust gas re-circulation gas flow
rate on the basis of a phase-difference time of a pressure waveform
at two or more positions measured by the pressure sensors, a
distance of the exhaust gas re-circulation passage between two or
more different pressure measurement positions and a sectional area
of the exhaust gas re-circulation passage of the heat exchanger.
According to the invention, it is possible to carry out the flow
rate measurement in a short response time without additionally
providing a pressure loss source.
[0005] According to another aspect of the invention, the measuring
equipment further includes: a second exhaust gas re-circulation gas
flow measuring unit which calculates a second exhaust gas
re-circulation gas flow rate on the basis of a difference between
pressure values measured at two or more different measurement
positions by the pressure sensors and the sectional area of the
exhaust gas re-circulation passage of the heat exchanger. According
to the invention, it is possible to simultaneously measure the
exhaust gas re-circulation gas flow rate by means of a plurality of
measurement methods and to determine whether the correction is
necessary by comparing the measurement values.
[0006] According to another aspect of the invention, the measuring
equipment further includes: a third exhaust gas re-circulation gas
flow measuring unit which calculates a third exhaust gas
re-circulation gas flow rate on the basis of a difference between
the intake air flow rate measured by the intake air flow sensor and
a predetermined value for each operation state of the internal
combustion engine. According to the invention, it is possible to
simultaneously measure the exhaust gas re-circulation gas flow rate
by means of a plurality of measurement methods and to determine
whether the correction is necessary by comparing the measurement
values. When the correction is necessary, it is possible to
estimate a damage state of the heat exchanger by back calculating a
sectional area value of the exhaust gas re-circulation passage of
the heat exchanger on the basis of the flow rate.
[0007] According to another aspect of the invention, the measuring
equipment further includes: a calculation unit which calculates a
quotient of a pressure difference between pressure values measured
at two or more measurement positions by the pressure sensors and an
amplitude of the pressure difference, and a difference between the
quotient and a predetermined value. According to the invention, it
is possible to estimate the measurement method having the highest
precision by comparing the above calculation result with a
previously researched relationship between measurement errors in
the respective measurement methods and the difference.
[0008] According to the invention, it is possible to measure the
exhaust gas re-circulation gas flow rate with high precision in a
short response time, and to accurately measure the exhaust gas
re-circulation gas flow rate even when the internal combustion
engine is transitionally operated. Accordingly, it is possible to
high-precisely set the internal combustion engine's output
performances such as fuel efficiency, nitrogen oxide, soot and
noise in such a manner that a comparison result between the exhaust
gas re-circulation gas flow rate measurement value and the exhaust
gas re-circulation gas flow rate target value is reflected in an
opening degree of the exhaust gas re-circulation gas flow control
valve.
[0009] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF DRAWINGS
[0010] FIG. 1 is an explanatory diagram illustrating a position
setting and a connection configuration of units necessary for a
measurement related to the invention.
[0011] FIG. 2 is an explanatory diagram illustrating an example in
which another sensor is attached to perform the measurement related
to the invention (Embodiment 1).
[0012] FIG. 3 is an explanatory diagram illustrating a method for
performing the measurement related to the invention (Embodiment
1).
[0013] FIG. 4 is an explanatory diagram illustrating the method for
performing the measurement related to the invention (Embodiment
1).
[0014] FIG. 5 is an explanatory diagram illustrating the method for
performing the measurement related to the invention (Embodiment
2).
[0015] FIG. 6 is an explanatory diagram illustrating the method for
performing the measurement related to the invention (Embodiment
2).
[0016] FIG. 7 is a flowchart illustrating a method for performing
the measurement related to the invention (Embodiment 3).
[0017] FIG. 8 is a flowchart illustrating another method for
performing the measurement related to the invention (Embodiment
4).
[0018] FIG. 9 is a flowchart illustrating another method for
performing the measurement related to the invention (Embodiment
5).
[0019] FIG. 10 is a flowchart illustrating another method for
performing the measurement related to the invention (Embodiment
6).
[0020] FIG. 11 is an explanatory diagram illustrating the method
for performing the measurement related to the invention (Embodiment
7).
[0021] FIG. 12 is an explanatory diagram illustrating the method
for performing the measurement related to the invention (Embodiment
8).
[0022] FIG. 13 is a diagram illustrating a relationship between a
correlation coefficient and a pulsation amplitude ratio.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Hereinafter, Embodiments according to the invention will be
described with reference to the accompanying drawings.
[0024] FIG. 1 is a configuration diagram illustrating a control
device for an engine according to Embodiment 1 of the invention.
Reference Numeral 19 shown in FIG. 1 denotes an engine. An air
cleaner 17, an air flow sensor 2, a compressor 6(b) of a
supercharger, an intercooler 16, a throttle 13 for adjusting an
intake air flow rate, an intake pipe 20, and a fuel injection valve
(hereinafter, an injector) 5 are arranged on the upstream side of
the engine 19. In this embodiment, an intake air flow controlling
unit includes the compressor 6(b), the intercooler 16 and the
throttle 13, and an intake air flow detecting unit includes the air
flow sensor 2. The injector 5 is configured to directly inject fuel
into a combustion chamber 18. It is desirable that the throttle 13
is an electronic control throttle which drives a throttle valve by
an electric actuator. In this embodiment, an intake pressure sensor
14 is disposed in the intake pipe 20 so as to appropriately control
an intake amount by detecting a pressure within the intake pipe 20.
An exhaust pressure/exhaust temperature sensor 3 is disposed in an
exhaust pipe 23. An exhaust gas re-circulation passage 9 for
re-circulating the exhaust gas to the intake pipe 20, an exhaust
gas re-circulation gas heat exchanger 10, and an exhaust gas
re-circulation gas flow control valve 11 are installed in the
exhaust pipe 23. In addition, the invention is characterized in
that an exhaust gas re-circulation gas pressure/temperature sensor
12 is disposed in the exhaust gas re-circulation passage 9 so as to
detect a pressure and a temperature of the exhaust gas
re-circulation gas. In this embodiment, the exhaust gas
re-circulation gas pressure/temperature sensor 12, the exhaust
pressure/exhaust temperature sensor 3, and the air flow sensor 2
are used to measure the exhaust gas re-circulation gas flow rate.
The injector 5 injects a predetermined amount of fuel in accordance
with target engine torque calculated by an opening degree signal
.alpha. output from an accelerator opening degree sensor 1, and
appropriately corrects the fuel amount in accordance with outputs
such as an opening degree signal .theta.tp output from the throttle
13, an opening degree signal .theta.egr output from the exhaust gas
re-circulation gas flow control valve 11, and a supercharge
pressure Ptin output from the compressor 6(b). Reference Numeral 8
denotes an engine control unit (hereinafter, ECU) which determines
a combustion mode or a control amount of the engine 19 in
accordance with a user request such as an accelerator opening
degree .alpha. or a brake state, a vehicle state such as a vehicle
speed, and an engine driving condition such as a temperature of an
engine cooling water or a temperature of exhaust gas.
EMBODIMENT 1
[0025] FIGS. 2 to 4 illustrate an exemplary measurement method
among the measurement methods according to the invention.
[0026] The drawings show the arrangement positions of the exhaust
gas re-circulation gas heat exchanger 10 for cooling the exhaust
gas re-circulation gas, exhaust pressure/exhaust temperature
sensors 3, 3', 3'', and the exhaust gas re-circulation gas
pressure/temperature sensors 12, 12', 12'' which are arranged at
two or more positions in the passage before and after the exhaust
gas re-circulation gas heat exchanger 10 so as to measure the
pressure and the temperature of the exhaust gas re-circulation
gas.
[0027] Since the measurement values of the temperature and the
pressure are used to calculate a sonic speed or a gas density, the
measurement needs to be carried out in a space having the same
condition. Thus, static pressure measurement portions 3(a), 3'(a),
3''(a), 12(a), 12'(a), 12''(a), positive-flow-direction dynamic
pressure measurement portions 3'(b), 3''(b), 12'(b), 12''(b), and
negative-flow-direction dynamic pressure measurement portions
3''(c), 12''(c) among pressure measurement portions and temperature
measurement portions 3(t), 3'(t), 3''(t), 12(t), 12'(t), 12''(t)
need to be respectively approximated to each other.
[0028] The measurement positions of the temperature measurement
portions 3(t), 3'(t), 3''(t), 12(t), 12'(t), 12''(t) are set to the
center of a passage section so as to measure an average temperature
of gas in space and the temperature measurement portions 3'(t),
3''(t), 12(t), 12'(t), 12''(t) are installed at two positions
before and after the heat exchanger 10. An average value in space
of the exhaust gas re-circulation gas as a measurement object
within the entire passage is obtained in such a manner that a sum
of the temperatures measured at two positions is obtained and a
quotient is obtained by dividing the sum by two, thereby reducing
an error of a measured temperature due to a heat loss by the heat
exchanger 10. The pressure measurement is carried out for the
purpose of a gas density calculation, a gas flow direction
determination, or a pressure loss detection and a pressure
propagation detection of the heat exchanger 10.
[0029] For this reason, in the minimum configuration shown in FIG.
2, the pressure measurement is carried out by the static pressure
measurement portions 3(a), 12(a) among the exhaust pressure/exhaust
temperature sensor 3 and the exhaust gas re-circulation gas
pressure/temperature sensor 12, and the above-described purpose is
attained by measuring only static pressure values before and after
the heat exchanger 10.
[0030] FIG. 3 shows a case that only the pressure propagation
detection is carried out by the positive-flow-direction dynamic
pressure measurement portions 3'(b), 12'(b) among the exhaust
pressure/exhaust temperature sensor 3' and the exhaust gas
re-circulation gas pressure/temperature sensor 12' installed before
and after the heat exchanger 10. Since pressure measurement holes
of the dynamic pressure measurement portions face the gas flow
direction, speed energy is changed into pressure energy in the
pressure measurement holes, and thus it is possible to obtain more
accurate amplitude signals. Accordingly, it is possible to improve
precision of a first exhaust gas re-circulation gas flow rate which
is measured by the use of a phase-difference time of a pressure
waveform, described in detail later. In addition, in a case that a
check valve is attached instead of the exhaust gas re-circulation
gas flow control valve 11 or a case that the exhaust gas
re-circulation gas flow control valve 11 is closed when it is
determined as a negative flow condition on the basis of a
difference between static pressure values measured before and after
the heat exchanger 10 by the exhaust pressure/exhaust temperature
sensor 31 and the exhaust gas re-circulation gas
pressure/temperature sensor 12', the negative-flow-direction flow
rate measurement is not necessary, and thus, the dynamic pressure
measurement is carried out only in an one-way direction. In this
case, the intake pressure and the exhaust pressure are
simultaneously measured by the exhaust gas/exhaust temperature
sensor 3 and the intake pressure sensor 14, and a control for
re-opening the exhaust gas re-circulation gas flow control valve 11
is carried out at the time point when the positive-flow-direction
condition is determined.
[0031] FIG. 4 shows a case that the flow rate can be measured in
the negative flow direction, where only the pressure propagation
detection is carried out by the positive-flow-direction dynamic
pressure measurement portions 3''(b), 12''(b) and the
negative-flow-direction dynamic pressure measurement portions
3''(c), 12''(c) among the exhaust pressure/exhaust temperature
sensor 3'' and the exhaust gas re-circulation gas
pressure/temperature sensor 12'' which are installed before and
after the heat exchanger 10. When it is determined as the
positive-flow-condition on the basis of a difference between static
pressure values measured before and after the heat exchanger 10 by
the exhaust pressure/exhaust temperature sensor 3'' and the exhaust
gas re-circulation gas pressure/temperature sensor 12'', the
pressure propagation detection is carried out by the measurement
pressure value obtained by the positive-flow-direction dynamic
pressure measurement portions 3''(b), 12''(b). In addition, when it
is determined as the negative-flow-condition on the basis of a
difference between static pressure values measured before and after
the heat exchanger 10 by the exhaust pressure/exhaust temperature
sensor 3'' and the exhaust gas re-circulation gas
pressure/temperature sensor 12'', the pressure propagation
detection is carried out by the measurement pressure value obtained
by the positive-flow-direction dynamic pressure measurement
portions 3''(c), 12''(c), thereby performing the high-precise flow
rate measurement of the exhaust gas re-circulation gas even in the
negative flow condition.
EMBODIMENT 2
[0032] FIGS. 5 and 6 show an exemplary flow rate calculation of the
exhaust gas re-circulation gas in the measurement methods according
to the invention. In FIG. 5, a phase time difference is set to a
time difference when the pressure waveforms measured at different
positions are compared with each other. Here, a speed at which
pressure propagates in gas having a gas flow corresponds to a value
obtained by adding a sonic speed to a gas flow speed. Accordingly,
it is possible to obtain the gas flow rate by using the following
expression:
[ Expression 1 ] Q ERG = ( L dt - .kappa. R ( T 1 + T 2 ) 2 )
.times. A .times. ( p 1 + p 2 ) R .times. ( T 1 + T 2 ) , formula 1
##EQU00001##
wherein
[0033] Q.sub.EGR[kg/h]: exhaust gas re-circulation gas mass flow
rate
[0034] L[m]: distance in an exhaust gas re-circulation passage
between two or more different pressure measurement positions
[0035] dt[sec]: phase-difference time
[0036] k[-]: specific heat ratio
[0037] R[J/kgK]: gas constant
[0038] T.sub.1[K]: temperature of exhaust gas re-circulation gas on
the upstream side of the exhaust gas re-circulation gas heat
exchanger
[0039] T.sub.2[K]: temperature of exhaust gas re-circulation gas on
the downstream side of the exhaust gas re-circulation gas heat
exchanger
[0040] A[m.sup.2]: sectional area of the exhaust gas re-circulation
passage
[0041] p.sub.1[Pa]: pressure of exhaust gas re-circulation gas on
the upstream side of the exhaust gas re-circulation gas heat
exchanger
[0042] p.sub.2[Pa]: pressure of exhaust gas re-circulation gas on
the downstream side of the exhaust gas re-circulation gas heat
exchanger.
[0043] FIG. 6 shows a relationship between the phase-difference
time and the flow rate upon applying the formula 1. With the
above-described method, it is possible to measure the exhaust gas
re-circulation gas flow rate without using the differential
pressure. Accordingly, it is possible to measure the exhaust gas
re-circulation gas flow rate even when the differential pressure
cannot be measured due to the low gas flow speed. Here, although
parameters except for the gas pressure, the gas temperature and the
phase-difference time are constant and are uniquely determined,
actually an error occurs due to a drift, a turbulence, a gas
component, humidity, and a heat exchange amount of the heat
exchanger 10. Accordingly, it is desirable that the correction is
carried out by simultaneously using another measurement method.
EMBODIMENT 3
[0044] FIG. 7 shows another exemplary flow rate calculation of the
exhaust gas re-circulation gas in the measurement methods according
to the invention. Since the flow speed is proportional to a value
obtained by a square root of the pressure difference between two
positions, it is possible to obtain the gas flow rate by using the
following expression.
[ Expression 2 ] Q = A .times. 2 R .times. .DELTA. p ( p 1 + p 2 )
( T 1 + T 2 ) formula 2 ##EQU00002##
[0045] Here, .DELTA.p[Pa]: pressure difference of exhaust gas
re-circulation gases before and after exhaust gas re-circulation
gas heat exchanger (=p.sub.1-p.sub.2).
[0046] FIG. 7 shows a relationship between the differential
pressure and the flow rate upon applying the formula 2. With the
above-described method, it is possible to measure the exhaust gas
re-circulation gas flow rate without using the pulsation component
of the pressure waveform. Accordingly, it is possible to measure
the exhaust gas re-circulation gas flow rate even when the
pulsation component of the pressure waveform cannot be detected
because a pressure loss is large between the pulsation component
generation source and the pressure measurement position. Here,
although parameters except for the gas pressure, the gas
temperature, and the differential pressure are constant and are
uniquely determined, actually an error occurs due to a drift, a
turbulence, a gas component, humidity, and a heat exchange amount
of the heat exchanger 10. Accordingly, it is desirable that the
correction is carried out by simultaneously using another
measurement method.
EMBODIMENT 4
[0047] FIG. 8 is a flowchart illustrating an exemplary flow rate
calculation procedure of the exhaust gas re-circulation gas in the
measurement method according to the invention.
[0048] The measurement method according to the invention is carried
out by periodically repeating the measurement and the
calculation.
[0049] First, the pressure value and the temperature value are
obtained by the exhaust pressure/exhaust temperature sensor 3 and
the exhaust gas re-circulation gas pressure/temperature sensor 12
which are installed before and after the heat exchanger 10 (Blocks
1001 and 1011).
[0050] Subsequently, a sonic speed is calculated by comparing with
a database stored in advance the pressure value measured at a
certain time in Block 1001 and the temperature value measured at a
certain time in Block 1011 (Block 1012).
[0051] Subsequently, a pulsation frequency is detected by
recognizing an interval (N shown in FIG. 5) between peaks of the
pressure waveform obtained by a history of the pressure value for a
predetermined time obtained in Block 1001 (Block 1002).
[0052] Subsequently, a band-pass frequency is set to a value
obtained by adding the pulsation frequency detected in Block 1002
to a predetermined constant in terms of an experiment, and
unnecessary noise components or undulation components are removed
by performing a band-pass filter process of the frequency to the
pressure waveform obtained by the history of the pressure value for
the predetermined time (Block 1003).
[0053] Subsequently, a history of the measurement pressure value
necessary for a phase comparison of the pressure waveform is
extracted. An extraction period is calculated from a quotient of a
predetermined cycle and the pulsation frequency detected in Block
1002, and a history of the measurement pressure value centering
around a certain time is extracted (Block 1004).
[0054] Subsequently, a pressure attenuation correction is carried
out. The pressure waveform on the downstream side of the heat
exchanger 10 obtained by the history of the pressure value
extracted in Block 1003 is attenuated by the pressure loss of the
heat exchanger 10. For this reason, for instance, when comparing
the phase of the peak of the pressure waveform on the upstream side
of the heat exchanger 10 with that of the peak of the pressure
waveform on the downstream side of the heat exchanger 10, it is
supposed that precision of the phase comparison deteriorates if the
pressure values at both peaks are different from each other.
Accordingly, a ratio between the amplitude before the attenuation
(a shown in FIG. 5) and the amplitude after the attenuation (b
shown in FIG. 5) is set to an attenuation ratio (a/b), and the
pressure attenuation correction is carried out by multiplying the
pressure value after the attenuation by the attenuation ratio so
that the maximum value and the minimum value of both pressure
values for a history are identical with each other. As a result, it
is possible to reduce deterioration of precision of the phase
comparison due to the attenuation (Block 1005).
[0055] Subsequently, a phase-difference time (dt1 shown in FIG. 5)
is detected. A time difference between a certain time (t1 shown in
FIG. 5) and a time at which the pressure value on the upstream side
of the heat exchanger 10 is identical with the pressure value
subjected to the attenuation correction on the downstream side of
the heat exchanger 10 at the above certain time is recognized. When
there are a plurality of the pressure values having the same value,
the phase-difference time is set to a time difference of which an
absolute value is the smallest (Block 1006).
[0056] Subsequently, a passage length value setting is carried out.
This corresponds to the gas passage length (L shown in FIG. 5)
between the pressure sensor attachment positions (Block 1013).
[0057] Subsequently, a pressure propagation speed calculation is
carried out. A quotient is obtained from a quotient of the
phase-difference time obtained in Block 1006 and the passage length
set in Block 1013 (Block 1007).
[0058] Subsequently, a flow speed calculation is carried out. A
difference is obtained between the pressure propagation speed
obtained in Block 1007 and the sonic speed obtained in Block 1012
(Block 1008).
[0059] Subsequently, a passage sectional area setting is carried
out. This corresponds to a gas passage sectional area in the heat
exchanger 10 (Block 1014).
[0060] Subsequently, a volume flow rate calculation is carried out.
A value is obtained by multiplying the flow speed obtained in Block
1008 by the passage sectional area obtained in Block 1014 (Block
1009).
[0061] Subsequently, a mass flow rate calculation is carried out.
Density of the exhaust gas re-circulation gas is obtained by a gas
constant calculated from the pressure value at a certain time
obtained in Block 1001, the gas temperature at a certain time
obtained in Block 1011, the component of standard exhaust gas
measured in advance by the experiment, and the humidity of the
standard exhaust gas measured in advance by the experiment, and is
multiplied by the volume flow rate obtained in Block 1009 (Block
1010).
[0062] In this way, it is possible to calculate the first exhaust
gas re-circulation gas flow rate.
EMBODIMENT 5
[0063] FIG. 9 is a flowchart illustrating an exemplary flow rate
calculation procedure of the exhaust gas re-circulation gas in the
measurement method according to the invention.
[0064] The measurement method according to the invention is carried
out by periodically repeating the measurement and the
calculation.
[0065] First, the pressure value and the temperature value are
obtained by the exhaust pressure/exhaust temperature sensor 3 and
the exhaust gas re-circulation gas pressure/temperature sensor 12
which are installed before and after the heat exchanger 10 (Blocks
1101 and 1108).
[0066] Subsequently, a pulsation frequency is detected by
recognizing an interval (N shown in FIG. 5) between peaks of the
pressure waveform obtained by a history of the pressure value for a
predetermined time obtained in Block 1101 (Block 1102).
[0067] Subsequently, a cut-off frequency of the filter is set to a
value obtained by multiplying the pulsation frequency detected in
Block 1102 by a predetermined constant in terms of an experiment,
and unnecessary noise components are removed by performing a
low-pass filter process to the pressure waveform obtained by a
history of the pressure value for the predetermined time (Block
1103).
[0068] Subsequently, a differential pressure is set to a pressure
difference at a certain time among history points of the pressure
waveform obtained in Block 1103 (Block 1104).
[0069] Subsequently, a flow speed is obtained from the pressure
value measured at a certain time in Block 1101 and the temperature
value measured at a certain time in Block 1108 and the differential
pressure at a certain time obtained in Block 1104 (Block 1105).
[0070] Subsequently, a passage sectional area setting is carried
out. This corresponds to a gas passage sectional area in the heat
exchanger 10 (Block 1109).
[0071] Subsequently, a volume flow rate calculation is carried out.
A value is obtained by multiplying the flow speed obtained in Block
1105 by the passage sectional area obtained in Block 1109 (Block
1106).
[0072] Subsequently, a mass flow rate calculation is carried out.
Density of the exhaust gas re-circulation gas is obtained by a gas
constant calculated from the pressure value at a certain time
obtained in Block 1101, the gas temperature at a certain time
obtained in Block 1108, the component of standard exhaust gas
measured in advance by the experiment, and the humidity of the
standard exhaust gas measured in advance by the experiment, and is
multiplied by the volume flow rate obtained in Block 1106 (Block
1107).
[0073] In this way, it is possible to calculate the second exhaust
gas re-circulation gas flow rate.
EMBODIMENT 6
[0074] FIG. 10 is a flowchart illustrating an exemplary flow rate
calculation procedure of the exhaust gas re-circulation gas in the
measurement method according to the invention.
[0075] The measurement method according to the invention is carried
out by periodically repeating the measurement and the
calculation.
[0076] First, the pressure value and the temperature value are
obtained by the exhaust pressure/exhaust temperature sensor 3 and
the exhaust gas re-circulation gas pressure/temperature sensor 12
which are installed before and after the heat exchanger 10 (Blocks
1201 and 1212).
[0077] Subsequently, a sonic speed is calculated by comparing the
pressure value measured at a certain time in Block 1201 and the
temperature value measured at a certain time in Block 1212 with a
database stored in advance (Block 1213).
[0078] Subsequently, a pulsation frequency is detected by
recognizing an interval (N shown in FIG. 5) between peaks of the
pressure waveform obtained by a history of the pressure value for
the predetermined time obtained in Block 1201 (Block 1202).
[0079] Subsequently, a cut-off frequency of the filter is set to a
value obtained by multiplying the pulsation frequency detected in
Block 1202 to a predetermined constant in terms of an experiment,
and unnecessary noise components are removed by performing a
low-pass filter process of the frequency to the pressure waveform
obtained by a history of the pressure value for the predetermined
time (Block 1203).
[0080] Subsequently, a history of the measurement pressure value
necessary for a phase comparison of the pressure waveform is
extracted. An extraction period is calculated on the basis of the
pulsation frequency detected in Block 1202 and a predetermined
cycle, and a history of the measurement pressure value centering
around a certain time is extracted (Block 1204).
[0081] Subsequently, a pressure attenuation correction is carried
out. The pressure waveform on the downstream side of the heat
exchanger 10 obtained by the history of the pressure value
extracted in Block 1204 is attenuated by the pressure loss of the
heat exchanger 10. For this reason, for instance, when comparing
the phase of the peak of the pressure waveform on the upstream side
of the heat exchanger 10 with that of the peak of the pressure
waveform on the downstream side of the heat exchanger 10, it is
supposed that precision of the phase comparison deteriorates if the
pressure values at both peaks are different from each other.
Accordingly, a ratio between the amplitude before the attenuation
(a shown in FIG. 5) and the amplitude after the attenuation (b
shown in FIG. 5) is set to an attenuation ratio (a/b), and the
pressure attenuation correction is carried out by multiplying the
pressure value after the attenuation by the attenuation ratio so
that the maximum value and the minimum value in the history of both
pressure values are identical with each other. As a result, it is
possible to reduce deterioration of precision of the phase
comparison due to the attenuation (Block 1205).
[0082] Subsequently, a phase-difference time (dt1 shown in FIG. 5)
is detected. A time difference between a certain time (t1 shown in
FIG. 5) and a time at which the pressure value on the upstream side
of the heat exchanger 10 is identical with the pressure value
subjected to the attenuation correction on the downstream side of
the heat exchanger 10 at the above certain time is recognized. When
there are a plurality of the time differences, the phase-difference
time is set to a time difference of which an absolute value is the
smallest (Block 1206).
[0083] Subsequently, a phase correction of the pressure waveform is
carried out. In order to correct the phase difference (dt shown in
FIG. 5) caused when the pressure propagates in the heat exchanger
10, the phase-difference time obtained in Block 1206 is added to an
upstream pressure measurement time (Block 1207).
[0084] Subsequently, a differential pressure is set to a pressure
difference at a certain time among history points of the pressure
waveform obtained in Block 1207 (Block 1208).
[0085] Subsequently, a flow speed is obtained from the pressure
value measured at a certain time in Block 1201, the temperature
value measured at a certain time in Block 1212 and the differential
pressure at a certain time obtained in Block 1208 (Block 1209).
[0086] Subsequently, a passage sectional area setting is carried
out. This corresponds to a gas passage sectional area in the heat
exchanger 10 (Block 1214).
[0087] Subsequently, a volume flow rate calculation is carried out.
A value is obtained by multiplying the flow speed obtained in Block
1209 by the passage sectional area obtained in Block 1214 (Block
1210).
[0088] Subsequently, a mass flow rate calculation is carried out.
Density of the exhaust gas re-circulation gas is obtained by a gas
constant calculated from the pressure value at a certain time
obtained in Block 1201, the gas temperature at a certain time
obtained in Block 1212, the component of standard exhaust gas
measured in advance by the experiment, and a gas constant
calculated from the humidity of the standard exhaust gas measured
in advance by the experiment, and is multiplied by the volume flow
rate obtained in Block 1210 (Block 1211).
[0089] In this way, it is possible to calculate the third exhaust
gas re-circulation gas flow rate.
EMBODIMENT 7
[0090] FIG. 11 is a flowchart illustrating another exemplary flow
rate calculation procedure of the exhaust gas re-circulation gas in
the measurement method according to the invention.
[0091] The measurement method according to the invention is carried
out by periodically repeating the measurement and the calculation
and by simultaneously calculating the first exhaust gas
re-circulation gas flow rate, the second exhaust gas re-circulation
gas flow rate, and the third exhaust gas re-circulation gas flow
rate by the use of the measurement values.
[0092] Here, the third exhaust gas re-circulation gas flow rate is
obtained as follows. First, an intake air flow rate 24
experimentally measured is stored in advance for each engine rpm as
well as the intake pressure value measured by the intake pressure
sensor 14 while the exhaust gas re-circulation gas flow control
valve 11 shown in FIG. 1 is closed. Subsequently, a difference is
obtained between the stored intake air flow rate 24 and an intake
air flow rate 24' measured when the exhaust gas re-circulation gas
flow control valve 11 is opened, so as to obtain the third exhaust
gas re-circulation gas flow rate by using the above difference.
[0093] Validity of the third exhaust gas re-circulation gas flow
rate is determined by a comparison of correlation data of the
engine rpm, the intake air flow rate, and the opening degree of the
exhaust gas re-circulation gas flow control valve 11, which are
obtained in advance by checking operations. When a large error
occurs, it is recognized that the driving state of the engine 19 or
the measurement equipment is abnormal.
[0094] First, the upstream pressure value of the heat exchanger 10
is compared with the downstream pressure value thereof (Block
1301).
[0095] Subsequently, when the comparison result obtained in Block
1301 satisfies the positive flow condition, the exhaust gas
re-circulation gas flow control valve 11 is opened (Block
1302).
[0096] Subsequently, when the comparison result obtained in Block
1301 satisfies the negative flow conciliation, the exhaust gas
re-circulation gas flow control valve 11 is closed (Block
1303).
[0097] Subsequently, when the exhaust gas re-circulation gas flow
control valve 11 is opened in accordance with the determination in
Block 1302, the first exhaust gas re-circulation gas flow rate is
compared with the third exhaust gas re-circulation gas flow rate
(Block 1304).
[0098] Subsequently, when a difference between the first exhaust
gas re-circulation gas flow rate and the third exhaust gas
re-circulation gas flow rate is not less than a predetermined value
(for instance, .+-.5% relative to the third exhaust gas
re-circulation gas flow rate) in accordance with the determination
in Block 1304, the exhaust gas re-circulation passage sectional
area value used to calculate the first exhaust gas re-circulation
gas flow rate is corrected so that both flow rates are identical
with each other (Block 1305).
[0099] Subsequently, when the exhaust gas re-circulation gas flow
control valve 11 is opened in accordance with the determination in
Block 1302, the second exhaust gas re-circulation gas flow rate is
compared with the third exhaust gas re-circulation gas flow rate
(Block 1306).
[0100] Subsequently, when a difference between the second exhaust
gas re-circulation gas flow rate and the third exhaust gas
re-circulation gas flow rate is not less than a predetermined value
(for instance, .+-.5% relative to the third exhaust gas
re-circulation gas flow rate) in accordance with the determination
in Block 1306, the exhaust gas re-circulation passage sectional
area value used to calculate the second exhaust gas re-circulation
gas flow rate is corrected so that both flow rates are identical
with each other (Block 1307).
[0101] Subsequently, when the exhaust gas re-circulation gas flow
control valve 11 is closed in accordance with the determination in
Block 1303, the second exhaust gas re-circulation gas flow rate is
compared with a predetermined value (Block 1308).
[0102] Subsequently, when it is determined that the second exhaust
gas re-circulation gas flow rate is larger than the predetermined
value in accordance with the determination in Block 1308, it is
recognized that the exhaust gas re-circulation gas flow control
valve 11 has a functional trouble (Block 1309).
[0103] Subsequently, when it is determined that the second exhaust
gas re-circulation gas flow rate is the predetermined value or less
in accordance with the determination in Block 1308, the first
exhaust gas re-circulation gas flow rate is compared with the
predetermined value (Block 1310).
[0104] Subsequently, when it is determined that the first exhaust
gas re-circulation gas flow rate is larger than the predetermined
value in accordance with the determination in Block 1310, the
exhaust gas re-circulation passage distance value between two or
more different pressure measurement positions used to calculate the
first exhaust gas re-circulation gas flow rate is corrected so that
the first exhaust gas re-circulation gas flow rate becomes 0 (Block
1311).
[0105] Subsequently, a quotient is obtained from a difference
between static pressures on the upstream side and the downstream
side of the heat exchanger 10 at a certain time and the amplitude
of the static pressure difference, and a difference is obtained
between the quotient and a predetermined value (Block 1312).
[0106] Subsequently, when the value obtained in Block 1312 is not
less than 0 or when it is recognized that the exhaust gas
re-circulation gas flow control valve 11 has the functional trouble
in Block 1309, the first exhaust gas re-circulation gas flow rate
is set to a calculation result (Block 1313).
[0107] Subsequently, when the value obtained in Block 1312 is
smaller than 0, the second exhaust gas re-circulation gas flow rate
is set to a calculation result (Block 1314).
EMBODIMENT 8
[0108] FIG. 12 is a flowchart illustrating another exemplary flow
rate calculation procedure of the exhaust gas re-circulation gas in
the measurement method according to the invention.
[0109] The measurement method according to the invention is carried
out by storing the calculation result while periodically repeating
the measurement and the calculation.
[0110] First, the first exhaust gas re-circulation gas flow rate,
the second exhaust gas re-circulation gas flow rate, and the third
exhaust gas re-circulation gas flow rate are calculated, and then
the calculation results are stored (Blocks 1401 to 1403).
[0111] Subsequently, a quotient is obtained from a difference
between static pressures measured at two or more positions at a
certain time by the pressure measuring portions of the exhaust
pressure/exhaust temperature sensor 3 and the exhaust gas
re-circulation gas pressure/temperature sensor 12 and the amplitude
of the static pressure difference, and then the quotient is stored
as the pulsation amplitude ratio (Block 1404).
[0112] Subsequently, calculation results for a predetermined number
of times are extracted from the calculation results stored in Block
1404, an average value of the extracted calculation results is
calculated, and then the calculation result is stored as an average
value of the pulsation amplitude ratio (Block 1407).
[0113] Subsequently, calculation results for a predetermined number
of times are extracted from the calculation results stored in
Blocks 1401 and 1402, a correlation efficient is calculated by a
least square method using the values of the first exhaust gas
re-circulation gas flow rate obtained in Block 1401 and the third
exhaust gas re-circulation gas flow rate obtained in Block 1402,
and then the calculation result is stored as a correlation
coefficient 1 (Block 1405).
[0114] Subsequently, calculation results for a predetermined number
of times are extracted from the calculation results stored in
Blocks 1402 and 1404, a correlation efficient is calculated by the
least square method using the values of the second exhaust gas
re-circulation gas flow rate obtained in Block 1403 and the third
exhaust gas re-circulation gas flow rate obtained in Block 1402,
and then the calculation result is stored as a correlation
coefficient 2 (Block 1406).
[0115] Subsequently, calculation results for a predetermined number
of times are extracted from the calculation results stored in
Blocks 1405 to 1407, and then an approximation line (a) (see FIG.
13) is obtained by the least square method using the values of the
average value of the pulsation amplitude ratio obtained in Block
1407 and the correlation coefficient 1 obtained in Block 1405. At
the same time, an approximation line (b) (see FIG. 13) is obtained
by the least square method using the values of the average value of
the pulsation amplitude ratio obtained in Block 1407 and the
correlation coefficient 2 obtained in Block 1406. Subsequently, a
pulsation amplitude ratio is obtained at a point where the
approximation line (a) intersects the approximation line (b), and
then the pulsation amplitude ratio is set to a selection
determination value (Block 1408).
[0116] Subsequently, it is determined whether the pulsation
amplitude ratio is larger than the selection determination value by
comparing the selection determination value obtained in Block 1408
with the pulsation amplitude ratio at a certain time obtained in
Block 1404. Subsequently, depending on the determined result, the
output value is changed into the first exhaust gas re-circulation
gas flow rate obtained in Block 1401 and the second exhaust gas
re-circulation gas flow rate obtained in Block 1403 (Block
1409).
EMBODIMENT 9
[0117] FIG. 13 is an exemplary method for selecting a high-precise
measurement method for flow rate of exhaust gas re-circulation with
respect to the pulsation amplitude ratio in Block 1408 of
Embodiment 8.
[0118] It is supposed that the measurement precision of the first
exhaust gas re-circulation gas flow rate and the second exhaust gas
re-circulation gas flow rate is concerned with the pulsation
amplitude ratio obtained from the quotient of the difference
between the static pressures on the upstream side and the
downstream side of the heat exchanger 10 and the amplitude of the
static pressure difference. For this reason, it is possible to
select the high-precise measurement method by obtaining the
relative correlation coefficients between the first and third
exhaust gas re-circulation gas flow rates, and between the second
and third exhaust gas re-circulation gas flow rates. In the example
shown in FIG. 13, the selection determination value is set to a
condition capable of measuring a pulsation amplitude ratio 100 in
which both approximation lines intersect with each other, and thus
the measurement method having high correlation coefficient is
selected. This is obtained in advance in terms of an experiment,
and is used as an initial value of the selection determination
value. Since the optimal value of the selection determination value
varies in accordance with a soiled and damaged state of the passage
in the heat exchanger 10, the selection determination value is
examined and corrected while a correlation estimation is carried
out whenever measuring the exhaust gas re-circulation gas flow rate
after starting the engine 19, thereby reducing deterioration in the
measurement precision of the exhaust gas re-circulation gas flow
rate.
[0119] The present invention is not limited to the application of
the internal combustion engine, but may be applied to a
high-precise pulsation flow meter as an industrial product in other
industrial fields.
[0120] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
* * * * *